A baby and a toddler were found dead after their mother put them both in the shower and fell asleep.
Miranda Hebble, who was 22 at the time of the tragedy, left her sons Lochlan and Malachi Stevens in the steam-filled bathroom at their house in Perth, Australia, for ten hours after she passed out.
When she woke up she discovered ten-month-old Malachi floating in the shower on his side with bruises on his cheek while Lochlan, two, was lying on the floor with blood coming from his mouth.
He also had a scratch on his forehead and a mark on his stomach, the court was told.
Ms Hebble had been caring for the boys at home alone while their father, Christopher Stevens, was working on a fly-in fly-out basis.
Lochlan had smeared faeces from his nappy on floors, walls and the baby's cot, spurring her to put the boys in the shower to clean them up.
She left to fetch something, closing the bathroom door behind her, but fell asleep before she could return, the inquest was told.
When she returned to the bathroom, some ten hours later, both children were dead.
Ms Hebble told an emergency services operator: 'I passed out and the plug in the shower got plugged up ... and the shower filled up ... and they're not breathing. They're dead.'
Doctors pronounced both boys dead at 2am the following morning.
Kate Ellson, counsel assisting the West Australia coroner, told the court that 'quiet' Ms Hebble had no history of mental illness or drug and alcohol abuse.
But she added that the young mother had struggled with sleep because of Malachi's restlessness.
The court also heard of a previous incident when Ms Hebble had left Malachi in a car while visiting a shop and the baby had to be pulled hot, crying and red in the face from the vehicle by police.
Ms Hebble told officers she had left him there because she was so exhausted she feared she might drop him if she tried to carry him, Miss Ellson said.
Post-mortem examinations could not reach a definitive conclusion as to how Ms Hebble's sons died in November 2008.
Drowning may have caused Malachi's death while Lochlan may have suffered exhaustion, hunger and possible hypothermia with exposure, said forensic pathologist Dr Jodi White.
Ms Hebble was comforted by family members as she watched proceedings. She and boys' father have now separated.
The inquest continues.